On the Mac you work on
When an update is ready, the menu says “Version … is available.” Click Install Update. You can also check yourself with Check for Updates… in Settings › About.
On the display Mac
The display Mac updates while it waits for your Mac, never while it shows a picture.
When the two versions don’t match
Each Mac updates on its own schedule. If their versions can’t work together, Second Display says so before any picture and names the Mac to update: “The other Mac needs an update” or “This Mac needs an update”. Update that Mac, then connect again.
Updates come from this website. Like any download, the request shows your IP address and the app’s version to our hosting provider.